DESCRIPTION (Principal Investigator's Abstract): This research continues an investigations of the concurrent, short-term, and long-term effects of nutritional intervention in the preschool years on bone development. This study will investigate the impact of a well-controlled nutritional supplementation project in Guatemala on skeletal maturation in young children, and in the same individuals when adolescents. Assessment of skeletal maturation are made from radiographs of the left hand and wrist, collected during a previous phase of the study. The findings on skeletal maturation will be considered with the applicants previous results on bone growth and mineralization to provide a comprehensive picture of the supplementation effects on various aspects of bone development. A parallel longitudinal data set of healthy U.S. children will be constructed as a comparison group for studying interrelationships among measures of bone growth and maturation, and of predictive relationships of adolescent status from bone status early in childhood. A focus of research will be the nature and degree of catch-up growth attending supplementation and the effects of supplementation on subsequent growth potential. The ability of chronically malnourished children to catch up in growth is in part related to the relative effects of nutritional treatments on linear growth compared with those on skeletal maturation. This research will help elucidate the relative roles of bone growth and maturation as determinants of catch-up growth and of final adult stature. These data, together with data on other aspects of physical growth, performance, and psychosocial development being collected by the Parent Project, will be analyzed to answer important questions relating to the permanency of nutritional intervention early in life. In addition, because of the unique nature of these data, the investigators should be able to address important questions relating other aspects of early childhood growth and nutritional status to later bone health.